Method for refining hydrocarbon oil containing mercaptans



Patented Sept. 19, 1933 METHOD FOR REFINING HYDROCARBON OIL CONTAINING MERCAPTANS Fred B. Behrens, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, 11]., a corporation of South Dakota No Drawing. Application October 24, 1930 Serial No. 491,086

2 Claims. (01. 196-33) This invention relates to the treatment of hydrocarbon oils and refers more particularly to the removal therefrom of compounds which render the oil sour and more particularly those which 5 give the general reactions of mercaptans including substances of a more or less similar nature which render the hydrocarbon mixtures unstable under the influence of light and/or heat.

More specifically the invention contemplates the use of various chemical reagents either alone or in combination to more effectively sweeten the light liquid products produced from the cracking of heavy hydrocarbon oils.

In a preferred embodiment of the invention pressure distillate of approximately gasoline boiling point range may be treated with an alkaline solution of sodium plumbite in any suitable apparatus, there being thereby produced from the mercaptans in the oil treated compounds with lead known as mercaptides which remain in solution in the oil.

Instead of the usual addition of free sulphur which is commonly used to split up the mercaptides into di-alkyl sulphides and lead sulphide, the present invention contemplates the use of alkaline oxidizing reagents containing compounds typified by potassium or-sodium or other permanganates. By the use of reagents of this class the available oxygen reactsto produce oxides instead oiv sulphides of lead which can be redissolved as such in caustic soda to produce sodium plumbite and thus used again in the initial sweetening step without substantial loss. An additional advantage is evident in that ordinarily when free sulphur is employed to finish the plumbite treatment it is practically always necessary to use the sulphur in excess in orderto completely break up the lead mercaptides as described, this excess of sulphur remaining dissolved in the oil 40 and tending to produce instability when the oil is exposed to light in an oxidizing atmosphere such as is usually encountered in visible dispensing pumps. This reaction which throws the gasoline oil color results also in the formation of definite amounts of sulphuric acid which causes discoloration of the gasoline and possibly corrosion in carbureters when the gasoline containing it is used. 50 In carrying out the operation of the process of the invention the oil to be treated is agitated with the plumbite solution; the excess of the latter withdrawn together with the reaction prodnets, and the oil is then treated with the permanganate solution after which the oil is freed from excess permanganate and reaction products, and is finally water washed.

In one example of the application of the process of the invention a sample of gasoline from the north Texas producing area was treated with sodium plumbite in amounts found necessary to react completely With the mercaptan sulphur present. When the treatment was completed by the usual addition of free sulphur followed by necessary settling and washing periods, the gasoline when exposed to sunlight for a certain period of time dropped in color from 26 to 16 measured on the Saybolt chromometer. When the break Was effected by the use of a dilute solution of potassium permanganate equivalent to 1% by volume of the oil treated, the corresponding drop in color after similar exposure to light was only from 26 to 22. In another case a gasoline from the Louisiana field was treated by the two methods just described. When the plumbite treatment was used with sulphur the color dropped from 24 to 16 on the Saybolt color scale after several days, exposure to sunlight. When treated first with plumbite and then with the permanganate solution the color dropped only to 21 under the same conditions of exposure.

It is evident from the preceding examples that a process has been disclosed which, when suitably applied, produces gasolines considerably more stable in color when exposed to light and air, and in addition has other advantages.

I claim as my invention:

1. A method for refining hydrocarbon oil containing mercaptans which comprises converting the mercaptans into lead mercaptides by treating the oil with plumbite solution, and then treating the oil with a permanganate to convert the mercaptides into oxide of lead.

2. In the sweetening of cracked hydrocarbon distillate containing mercaptans, the steps which comprise treating the distillate with plumbite solution to convert the mercaptans into oil-soluble lead mercaptides, separating excess plumbite solution and accompanying reaction products,

and then treating the distillate with permanganate to convert the mercaptides into oxide of lead.

FRED B. BEHRENS. 

